Sewer drain is lower than the dump drain.

This is a problem that all owners of coaches like mine face. (once 12K+ now only about 9K after 40+ years) Many have installed macerator pumps and dealt with the reliability that is way lower than gravity. I thought about carrying a portable macerator of some kind, but without any external storage, I would not know where to keep it. Most of the better campgrounds have the dump at grade, so they are no problem. If we are at a campground (we rarely are) and they have the pipe sticks up, I look for another slip to go to.

In short, I don't have any good answer for you.

Matt